This invention relates to an optical disk drive and an optical head used therein.
Generally, an optical disk drive has an optical head for writing data on and/or reading data from an optical disk. The optical head includes a rotary arm which is rotatable along a surface of the optical disk. The rotary arm carries a light source module that emits light and an object lens that converges the light on the optical disk.
However, since the light source module is mounted on the rotary arm (as well as the object lens), the rotary arm is relatively heavy. It prevents an improvement of accessing speed of the rotary arm.
Further, there is an optical head including a pair of rotary arms respectively faced with both surfaces of a xe2x80x98double-sidedxe2x80x99 optical disk. In such an optical head, each rotary arm carries its own light source module and object lens. Thus, the rotary arms are relatively heavy.
It is therefore an object of the present invention to lighten a rotary arm of an optical head.
For the above object, according to one aspect of the present invention, there is provided an optical head including (1) a stationary optical unit fixed to a stationary part of an optical disk drive, including a light source module which emits light, (2) a rotary arm which is rotatable along an optical disk, which carries an object lens which converges the light on the optical disk, and (3) a light-introducing system which introduces the light from the light source module to the rotary arm so that the light proceeds in the rotary arm and reaches the object lens.
As constructed above, since the light source module is not mounted on the rotary arm but mounted on a stationary part of the optical head, the rotary arm (movable part of the optical disk) is lightened. It is advantageous in an improvement of the accessing speed of the optical head.
In a particular arrangement, the light-introducing system comprising a first reflection mirror which reflects the light from the light source module to a direction toward the rotary arm. The light-introducing system includes a second reflection mirror provided to the rotary arm, which reflects the light from the first reflection mirror to an optical path of the rotary arm. The light path between the first and second reflection mirrors is aligned with the rotation axis of the rotary arm.
Due to the first and second reflection mirrors, the light from the light source module is introduced into the rotary arm, irrespective of the rotational position of the rotary arm.
In a further development, the first reflection mirror is a so-called galvano mirror which is rotatable about an axis positioned on a reflection surface thereof. By rotating the galvano mirror, an incident angle on the object lens is varied by a rotation of the galvano mirror, so that a light spot formed on the optical disk is minutely moved. With this, a fine tracking operation is accomplished. With such an arrangement, one mirror is commonly used for the fine tracking operation and for the introduction of the laser beam to the rotary arm.
Advantageously, the rotary arm carries at least two relay lenses. The relay lenses are provided between the first reflection mirror and the object lens to obtain a conjugate relationship between a principal plane of the objective lens and a rotation axis of the first reflection mirror. With this, the laser beam reflected by the first reflection mirror is surely enter the objective lens irrespective of the rotating of the first reflection mirror.
In a preferred embodiment, the rotary arm is positioned between the stationary optical unit and the optical disk in the direction of the rotation axis of the rotary arm. It is alternatively possible that the rotary arm and the stationary optical unit are located at the same side of the optical disk.
In another aspect of the present invention, there is provided an optical head including (1) an optical unit including a light source module which emits light, (2) at least a pair of rotary arms that are rotatable along the optical disk, each of which carries an object lens which converges the light on the optical disk, and (3) a switching system which selectively introduces the light from the light source module to one of the rotary arms, so that the light proceeds in the selected rotary arm.
With such an arrangement, since a common light source module can be used for two rotary arms, the rotary arms are lightened. It is advantageous in an improvement of the accessing speed. Further, since at least one light source module is not needed, the number of optical elements is reduced.
It is advantageous that the optical unit is fixed to a stationary part of the optical disk drive. With this, the rotary arms are further lightened. In particular, the rotary arms are mounted in a rotatable carriage.
In a preferred embodiment, the switching system including (1) a first reflection mirror provided to the optical unit, which reflects the light from the light source module, and (2) second reflection mirrors respectively provided to the rotary arms, each of which is able to reflect the light from the first reflection mirror to a direction along a longitudinal direction of the rotary arm. The light path between the first reflection mirror and each of the second reflection mirrors is aligned with the rotation axis of the rotary arms.